The present invention pertains to a power converter and, more particularly, to a power converter of the type utilized to provide DC power to the electrical system of a recreational vehicle.
Power converters for converting AC power to a regulated DC level are well known. Low cost power converters typically comprise a DC voltage regulator which controls the output voltage to be near a predetermined level. However, the output voltages of these power converters include large ripples. This instability limits the type of motors which can be used in the recreational vehicle. Accordingly, relatively costly DC motors, which operate properly with a power supply which is not stable, are used in recreational vehicles so that low cost DC voltage regulators may be employed as the DC power converter for the recreational vehicle electrical system.
An alternative to the DC voltage regulators used in recreational vehicles are switched power converters. Switched power converters have a more stable supply voltage at their outputs. However, the switched power converter circuitry required to produce the more stable output voltage is costly.
Known switched power converters generating a sufficiently high power output that they could be used for recreational vehicle applications have stringent heat dissipation requirements which are severely restrictive to recreational vehicle manufacturers. If known switched power converters are positioned too close to a heat source, vehicle thermal insulation, or any other item which limits the power converter's ability to dissipate heat, the heat generated during normal operation of the switched power converter may destroy it or ignite nearby items causing a fire in the recreational vehicle. Even if the operating temperature of the power converter is not high enough to cause severe damage to the power converter, an inability to adequately dissipate heat in a recreational vehicle application can severely limit the operating life of the switched power converter.
An additional difficulty with known switched power converters is that they are physically large. Switched power converters are large because of the substantial surface area required to accommodate all the converter components, and because the housing is used to dissipate the heat which is generated by the energy storage components and switches employed therein. Although recreational vehicles vary widely in size, they are typically densely packed to provide a large amount of household type furnishings in a small space. Accordingly, the amount of space available for the power converter is limited, which makes it particularly difficult to find a suitable mounting location for the switched power supply.
Another difficulty encountered in providing switched power converters in recreational vehicles is that switched power converters do not include adequate protection against a reverse battery connection. Recreational vehicles typically include an independent power supply, such as batteries, which are used to supply power to the vehicle when a main power supply is not available. These batteries are often disconnected when the recreational vehicle is stored. When the vehicle is removed from storage, the vehicle owner reconnects the batteries to the vehicle electrical system. If the positive and ground output terminals of the power converter are connected to the battery negative and positive terminals, a reverse battery condition occurs. In prior art switched power circuits, such a reverse battery condition destroys the power converter switching elements, which cannot handle the resulting large current flow.
The large dimensions and the limited heat dissipating ability of known switched power converters noted above greatly restrict recreational vehicle manufacturers. An additional restriction presented by known switched power converters is that they include a fan for cooling the circuit. These fans generate undesirable noise at night when people are trying to sleep in the recreational vehicle. Accordingly, recreational vehicle designers must place the power supply at a location where the cooling fan will not disturb occupants of the vehicle while they are falling asleep.